The present invention relates generally to the manufacture of interconnect structures, and more particularly to the formation of self-aligned dielectric caps on copper interconnects.
Dielectric caps are employed in copper interconnects to act as a copper diffusion barrier. Dielectric caps may also act as an oxygen diffusion barrier to prevent oxidation of copper. Dielectric caps ensure good electromigration performance; however, the dielectric constant of conventionally used dielectric caps such as silicon carbide (SiC) and silicon carbon nitride (SiCN) is high (e.g., 5-7). The dielectric cap substantially contributes to Resistive Capacitive (RC) delay. It is desired to have a self-aligned dielectric cap for capacitance reduction and performance improvement.